Low Balance Pressure Reduction Alarm; Low Balance Pressure Reduction Shutdown; Low Discharge Temperature Difference Alarm; High Suction Pressure Gradient Alarm - Johnson Controls SABROE UniSAB III Engineering Manual

Alarms and shutdowns
The high oil balance pressure reduction supervision function is operative when the compressor is
running.
2.2.42

Low balance pressure reduction alarm

This alarm is released if the calculated balance pressure reduction P
is lower than the low alarm limit. See Table 9.
2, abs
The low oil balance pressure reduction supervision function is operative when the compressor is running
and the Balance pressure reduction function is active, i.e. the AUX output is OFF, and with a delay of 5
sec.
2.2.43

Low balance pressure reduction shutdown

This shutdown is released if the calculated balance pressure reduction P
is lower than the low shutdown limit. See Table 9.
press_2, abs
The low oil balance pressure reduction supervision function is operative when the compressor is running
and the Balance pressure reduction function is active, i.e. the AUX output is OFF, and with a delay of 5
sec.
2.2.44

Low discharge temperature difference alarm

This alarm is released if the calculated discharge temperature difference T
than the low alarm limit. See Table 9.
The low discharge temperature difference supervision is operative when the compressor is running at
"Full capacity", which is defined as Yield >/= 98 %.
With a hysteresis of 5.0 %, this means that the alarm supervision must be activated when Yield >/= 98%
and deactivated when Yield < 93%.
The low discharge temperature difference alarm is delayed at compressor start by the timer Discharge
diff. start. After the Discharge diff. start timer has run out, the alarm is further delayed during operation
by the timer Discharge diff. delay, see Table 52.
2.2.45

High suction pressure gradient alarm

This alarm is released if the calculated suction pressure gradient P
the high alarm limit. See Table 9 and Table 15.
The suction pressure gradient supervision function is operative when the compressor is running.
2.2.46

High suction pressure gradient shutdown

This shutdown is released if the calculated suction pressure gradient P
than the high alarm limit. See Table 9 and Table 15.
The suction pressure gradient supervision function is operative when the compressor is running.
2.2.47

High separator flow (screw compressor)

This function limits the compressor capacity to a calculated limit at certain running conditions. When the
difference pressure across the compressor is too low, the capacity is limited in order to protect the unit
against oil carry-over to the system.
2.2.48

High liquid level (reciprocating compressors)

This alarm is released if the capacity limiting function is active. The high liquid limiter will reduce com-
pressor capacity as long as the liquid level is high in the evaporator. When the liquid level is back to nor-
mal, and after the Liquid level delay has timed out, the alarm is reset.
Engineering manual - UniSAB III 1.10.8
001930 en 2021.06
bal_press_red, rel
suct_grad
suct_grad
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= P – P
disch, abs oil_press_
= P
bal_press_red, rel disch, abs
= T – T is lower
disch_diff disch oil
= dP /dt is higher than
suct, abs
= dP /dt is higher
suct, abs
– P
oil_